Gear Pump

ABSTRACT

A gear pump has a face plate  2  cooperating with central plate  24  defining a pump chamber  21  holding gears  16.  The pump chamber  21  is in fluid communication with drive chamber  32  holding the rotor  40  of an electric motor. An O-ring  18  may be used to seal the face plate  2 . Other elements may be sealed using a permanent seal such as glue.

FIELD OF INVENTION

The invention relates to a gear pump.

BACKGROUND OF THE INVENTION

A gear pump is a type of pump in which two intermeshed gears rotate within a chamber. The teeth of the gears entrain liquid between the gears and the inner surface of the chamber and as the gears rotate pump liquid in the chamber is pumped from an inlet to the chamber to an outlet to the chamber.

Gear pumps can be used in many applications. Of particular interest are applications where long term reliability is required, for example where a pump is to be installed in a location where access is difficult, making service or replacement difficult, or in a consumer product where long term reliability avoids product failure and customer dissatisfaction.

There is accordingly a need for gear pumps that are designed for long life.

SUMMARY OF INVENTION

According to the invention there is provided a gear pump for pumping a pump fluid, comprising:

a pump chamber having a first port and a second port, and a pair of gears mounted for rotation in the pump chamber for driving pump fluid from the inlet to the outlet;

a motor comprising a rotor and a drive shaft connected to the rotor to drive the pair of gears, the drive shaft and rotor being arranged in a drive chamber, the motor further comprising a stator arranged around the drive chamber;

wherein the pump chamber and the drive chamber are in fluid communication to allow pump fluid to pass between them.

In this way, the pump fluid can provide lubrication for the rotor in the drive chamber.

The inventors have realised that it is not necessary to completely seal the chamber of a gear pump from a motor, and that by not doing so the longevity of the pump can be improved.

In an embodiment, the gear pump includes a face plate having the first port and the second port; an inner plate, the inner plate and the face plate defining the pump chamber between them; a seal around the pump chamber between the inner plate and the face plate, for example an O-ring, and the inner plate has a central opening within the seal to provide a fluid path between the pump chamber and the drive chamber and wherein the drive shaft passes through the central opening to drive the gears.

In this way, the pump chamber is sealed with a removable seal so that the pump can be manufactured by providing suitable gears and then mounting the face plate to the inner plate and sealing.

A motor plate may be provided on the opposite end of the gear pump to the face plate, the stator being provided between the motor plate and the rotor plate. The stator may be a sealed unit extending around the drive chamber, one end of the drive chamber being sealed by the motor plate and the other end of the drive chamber being externally sealed against the motor plate.

The motor chamber may sealed with a permanent seal, since it is not generally necessary to provide separate access. The permanent seal may be glue.

Screws passing through the motor plate and face plate may be used to compress the motor plate towards the face plate to hold the gear pump together.

Conveniently, the screws may pass longitudinally through flanges extending radially outwards from the inner plate and motor plate.

BRIEF DESCRIPTION OF DRAWING

For a better understanding of the invention, an embodiment will now be described, purely by way of example, with reference to the accompanying drawing.

FIG. 1 shows an exploded perspective view of a gear pump according to an embodiment of the invention.

DETAILED DESCRIPTION

A face plate 2 is formed to have opposed flanges 4 and through holes 6, 8 which function as ports to the gear pump. Location through holes 14 are provided for location pins 28 which keep the different components of the gear pump in alignment.

An O-ring seat 10 is formed on the inner face of the face plate 2, together with axle holes 12 for holding axle 26 and drive shaft 48 which support gears 16.

Inner plate 20 has central cutout 22 for holding the gears 16 as well as location through holes 14.

Central plate 24 has a central through hole 26 for the drive shaft 48 as well as location through holes 14 and an axle hole 12 for holding axle 26 supporting one of the gears 16.

Stator 30 is mounted on central plate 24 and is a fully sealed unit arranged as a cylinder around a central drive chamber 32. The stator 30 includes a plurality of electrical coils. Motor plate 34 forms the opposite end of the gear pump to face plate 2 and is provided with flanges 36 with threaded through holes 38.

Rotor 40 is shaped to rotate inside the drive chamber 32 and mounted on bushes 42, one of which is mounted in motor plate 34 and the other of which is in central plate 24.

The gear pump is held together with screws 44 which pass through the flanges 4 on the face plate 2 and screw into the threaded holes 38 on motor plate 34. A pump chamber 21 is formed, sealed by O-ring 18 in O-ring seat 10 which defines the lateral extent of the pump chamber 21 and allows the face plate 2 to be assembled separately during manufacture. This allows the use of different gears for different applications.

Inlet 46 and outlet 47 mountings with end fittings for a tube are mounted to connect to inlet and outlet ports 6, 8.

One of the gears 16 is mounted on axle 26, the axle 26 having one end supported on axle hole 12 in the face plate 2 and the other on axle hole 12 in the central plate 24.

The other gear 16 is mounted on the drive shaft 48 which has one end supported on the other axle hole 12 in the face plate 2 and which is connected to the rotor 40.

The face plate 2, inner plate 20 and central plate 24 are kept in alignment by location pins 28 passing through location through holes 14 in those plates.

The motor, i.e. the central plate 24, stator 30 and motor plate 34 are sealed using glue. Further, the central plate 24 is sealed to the inner plate 20 with glue.

In use, the stator 30 is driven electrically to drive rotor 40 which turns the gears 16 in the pump chamber 22 to pump fluid from the inlet to the outlet.

Conventionally, seals have been provided in gear pumps to fully seal the motor from the pump chamber. In the present case however a fully sealed stator 30 is used, the drive chamber 32 in which the rotor 40 sits is sealed by motor plate 34 but there is no seal along drive shaft 48 between the pump chamber 22 and the drive chamber 32.

This allows fluid to enter the drive chamber 32 to act as a lubricant.

The design is arranged for easy manufacture using standard components. Indeed, the various component parts are commercially available. In particular, the motor formed by the central plate 24, stator 30, drive rotor 40 and motor end plate 34 is commercially available.

Further, the use of glue for the motor to seal inner plate 20, central plate 24, stator 30 and motor plate (34) is cheap and provides an efficient seal while the use of an O-ring to seal the pump chamber allows for flexible manufacturing with different gears for different applications.

The design delivers a reliable long life by the use of a brushless electric motor.

Those skilled in the art will realise that different components, plates and motors may be substituted for those described above. 

1. A gear pump for pumping a pump fluid, comprising a pump chamber (21) having a first port (6) and a second port (8), and a pair of gears (16) mounted for rotation in the pump chamber for driving pump fluid between the first port (6) and second port (8); a motor comprising a rotor (40) and a drive shaft (48) connected to the rotor to drive the pair of gears, the drive shaft and rotor being arranged in a drive chamber (32), the motor further comprising a stator arranged around the drive chamber (30); wherein the pump chamber (21) and the drive chamber (32) are connected to allow pump fluid to pass between them.
 2. A gear pump according to claim 1, comprising: a face plate (2) having the first port (6) and the second port (8); an central plate (24), the central plate (24) and the face plate (2) defining the pump chamber (21) between them; wherein the central plate (24) has a central opening to provide a fluid path between the pump chamber and the drive chamber and wherein the drive shaft passes through the central opening to drive the gears.
 3. A gear pump according to claim 2 further comprising an inner plate (22) sealed to the face plate with an O-ring (18).
 4. A gear pump according to claim 2, further comprising a motor plate (34) on the opposite end of the gear pump to the face plate, the stator (30) being provided between the motor plate (34) and the central plate (24).
 5. A gear pump according to claim 4, wherein the stator (30) is a sealed unit extending around the drive chamber (32), one end of the drive chamber being sealed by the motor plate (34) and the other end of the drive chamber being externally sealed against the central plate (24).
 6. A gear pump according to claim 4 wherein the central plate (24) and motor plate (34) are sealed to the stator (30) with a permanent seal.
 7. A gear pump according to claim 6 wherein the permanent seal is glue.
 8. A gear pump according to claim 4, further comprising a plurality of screws (44) passing through the motor plate (34) and face plate (2) arranged in tension to hold urge the face plate (2) towards the motor plate (34).
 9. A gear pump according to claim 8 wherein the face plate (2) and the motor plate (34) have flanges (4,36) extending radially outwards from the plate, the screws (44) passing through the flanges. 